The unnoticed melt

“Well, it’s not really good timing to write about global warming when the summer feels cold and rainy”, a journalist told me last week. Hence, at least here in Germany, there hasn’t been much reporting about the recent evolution of Arctic sea ice – despite the fact that Arctic sea ice extent in July, for example, was the lowest ever recorded for that month throughout the entire satellite record. Sea-ice extent in August was also extremely low, second only to August 2007 (Fig. 1). Whether or not we’re in for a new September record, the next weeks will show.

Figure 1: Evolution of Arctic sea-ice extent in July and August from 1979 until 2011. (NSIDC)

A rainy summer might be one reason for an apparent lack of public attention with respect to the ongoing sea-ice loss. Another reason, however, is possibly the fact that we scientists have failed to make sufficiently clear that a major loss of sea ice during the early summer months is climatologically more important than a record minimum in September. This importance of sea-ice evolution during the early summer months is directly related to the role of sea ice as an efficient cooling machine: Because of its high albedo (reflectivity), sea ice reflects most of the incoming sunlight and helps to keep the Arctic cold throughout summer. The relative importance of this cooling is largest when days are long and the input of solar radiation is at its maximum, which happens at the beginning of summer. If, like this year, sea-ice extent becomes very low already at that time, solar radiation is efficiently absorbed throughout all summer by the unusually large areas of open water within the Arctic Ocean. Hence, rather than being reflected by the sea ice that used to cover these areas, the solar radiation warms the ocean there and thus provides a heat source that can efficiently melt the remaining sea ice from below. In turn, additional areas of open water are formed that lead to even more absorption of solar radiation. This feedback loop, which is often referred to as the ice-albedo feedback, also delays the formation of new sea ice in autumn because of the accompanying surplus in oceanic heat storage.

Measurements from ice buoys show that indeed melting at the bottom of the sea ice has increased significantly in recent years. While field experiments that were carried out in the 20th century showed unambiguously that surface melting used to be the dominant mechanism for the thinning of Arctic sea ice, now in larger and larger areas melting at the underside of the ice is almost equally important. Such melting from below is particularly efficient since the temperature at the ice-ocean interface is fixed by the phase equilibrium that must be maintained there. Hence, any heat provided by the ocean to this interface will lead to thinning of the ice in summer and to slower ice growth in winter. At the surface, the ice temperature is not fixed as long as the ice isn’t melting, and heat input from the atmosphere can in part be compensated for by a change in surface temperature and an accompanying change in outgoing long-wave radiation at the ice surface.

In addition to these climatological reasons, there is another reason for why a public focus on just the September sea-ice extent is possibly misleading: Such focus might give the impression that sea-ice extent is stable in other seasons but summer. That this is not the case becomes obvious from the graphical distribution of extreme sea-ice extent for each individual month that is shown in Figure 2. The figure shows in red the years with the five lowest values of sea-ice extent for a certain month and in blue the years with the five highest values. A retreat of sea ice throughout the entire year is obvious. In fact, the sea-ice extent for every month since June 2010 has been among the five lowest values ever recorded by satellites.

Figure 2: Distribution of record minima and record maxima of Arctic sea-ice extent (NSIDC). The years with the five lowest values of sea ice extent for a certain month are marked in red, those with the five highest values of sea-ice extent are marked in blue. The darkness of the color indicates the ranking: the darkest red marks the lowest value, the darkest blue the highest.

Such widespread loss of Arctic sea ice has sometimes given rise to the concern that the total loss of Arctic sea ice at least during summer time can no longer be avoided. In this context, usually the ice-albedo feedback is mentioned, since it provides a mechanism that can in principle lead to a so-called “tipping point” beyond which the loss of the remaining sea ice becomes unstoppable. However, recent research shows that this scenario is too pessimistic. For example, in a paper published in Geophysical Research Letters in January 2011, Tietsche et al. [1] used climate model simulations to examine the evolution of Arctic sea ice after an extreme loss event. In their model simulations, they artificially removed all Arctic sea ice at the beginning of June for selected years and examined if the ice would recover from such extreme event.

Their main result is shown in Fig. 3: It took only about two years after each complete sea-ice removal until the ice had recovered to roughly the extent it had before the removal. Hence, sea ice extent is primarily defined by the prevailing climate conditions; the ice-albedo feedback mechanism is, in isolation, too weak to stabilize a very low sea-ice cover. In examining the mechanisms behind this finding, Tietsche et al. found that unusually large amounts of heat indeed accumulate in the ocean during the ice-free summer. However, this heat is efficiently released to the cold atmosphere already during the following autumn and winter. Once that heat release has cooled the ocean to its freezing temperature, sea ice forms again. Because this ice is initially very thin, the efficient release of heat from the ocean continues for some time, causing a rapid growth of the new sea ice. Much of this ice then survives the following summer, and sea-ice conditions can quickly return to those before the artificial perturbation.

Figure 3: Evolution of September sea-ice extent in coupled climate model simulations. The blue curve shows the evolution of the unperturbed sea-ice extent for the A1B scenario, with the gray shading showing the ensemble spread of three model runs. For the red curves, sea ice was artificially removed at the beginning of June in 1980, 2000, 2020, 2040 and 2060 within the climate model simulations. For all these perturbations, sea-ice extent recovered rapidly to the unperturbed extent. A similar result was found for sea-ice volume.

The finding that the long-term evolution of Arctic sea ice is primarily governed by the prevailing climate conditions implies that the loss of Arctic sea ice can still be slowed down and eventually stopped if an efficient reduction of CO2 emissions were to become reality soon. Last week, however, it became obvious once more how unlikely such scenario is: On 30th August, Exxon announced a deal with Rosneft, the Russian state oil company. As part of this deal, Exxon will invest more than US$2 billion to support Rosneft in the exploitation of oil reserves in the Kara Sea, which is part of the Arctic Ocean north of Siberia. One requirement for the success of this deal: a further retreat of Arctic sea ice. Given that climate model simulations indeed all project such further retreat of Arctic sea ice, it seems that at least to some degree, managers of big oil companies have started to make business decisions based on climate-model simulations. That may be good news. Or not.

This article is in part based on a German article that was published at Klimalounge.

Bruce, that is a good point, very similar to Roger Pielke Sr.’s insistence that global temperature series is an inferior metric to ocean heat content, except that our records of sea ice extent go back much further and are better calibrated than for volume, as our records of global temperature go back much further. The perfect is often enemy of the excellent.

This is an interesting piece about the importance of feedback mechanisms in the Arctic. From the last few lines a very ironic conclusion can be drawn: there is not only an ice-albedo feedback, but (at least theoretically) also an ice – fossil-fuel-exploration feedback.

The ice volume change is less relevant to the ice-albedo feedback, where the relative proportions of ice covered to ice free ocean dominate the radiative effect. Reducing ice thickness (volume) will serve to make the system more sensitive to melting (and further area loss and radiative feedback) but as mentioned in the Tietsche et al paper this will be rapidly recovered from.

The USGS estimates an equivalent of 3 years of current world wide human oil consumption in the Arctic which is close to one year of all anthropogenic CO2 emissions into the atmosphere; not counting trillions of cubic feet of natural gas also assumed in the Arctic. I wonder whether the forcing of this additional positive feedback effect evoked by exploited Arctic resources has been included in the model shown above.

However, the model run of 2060 substantiates sea ice can not recover once the climate is ruined. The Kara Sea was already ice free very early this year. Is it just irony best adaptor to a changing climate is the oil industry? Ultimately it is up to me to choose a clean energy provider.

So Exxon, who already benefits through unabated fossil fuel sales bought by continued FUD from contrarians, has another reason to buy some more FUD from contrarians in order to shrink the Arctic sea ice cover some more and increase its profits from the Arctic Rosneft deal.

Sounds like a good time to enter the professional contrarian business… Does anyone know of an Exxon contact who I can send my CV to get a FUD grant?

Given the continuous and quickening ice volume decrease it looks like the ice is unstable in _present_ conditions. In other words, in present climate conditions a late summer ice pack cannot exist, nor recover from artificial removal.

In fact, no realistic emission reduction scenario is going to prevent us from witnessing a first ice free Arctic summer before the year 2020.

A Schwarzenfeld is a massive negawatt event caused by a perfect storm of Greenwashing led by a Governor and an Energy Commission.

A negawatt event is when power produced is reduced. For those capable of subtracting, it is what happens when something stops and you subtract the output that is thus ended.

During the time of the Schwarzenfeld the developed world in Southern California, from Arizona to the Sea and from Orange County into Mexico, reverted to an ancient, primitive condition. At first the phenomenon exhibited as general paralysis of society as demonstrated by traffic grid-lock and disablement of all civilized mechanisms for food preparation leaving hapless folk with only that which could be done by means of that ancient device known as fire. This deteriorated further into a condition known as darkness with some modification from candlelight. The sense of doom was then lifted and a measure of hope for the future returned to the dismayed peoples with observations of a round thing in the sky, hitherto obscured by city lights, known as a moon.

A spokesman for the local SDGE has repeatedly explained that the problem was due to an ‘event’ in Arizona which was aggravated by inadequate transmission lines. He seemed not aware of the effect of the State of California having banned coal as a fuel for making electricity, thus removing the backbone power source that could once have been depended on to keep the electric grid system provided with energy.

Some of us have done back-of-the-envelope calculations (i.e. amateurishly simple and wrong) calculations of the effects of albedo loss in terms of terawatts of power being dissipated in summertime Arctic waters that otherwise would have been reflected back into space. For many of us (me) it’s helpful to our intuitions to be able to think of these matters in terms of 100W lightbulbs, familiar sizes of electric motors or whatever; many of us can relate to KWH thanks to paying electrical utility bills.

I vaguely remember getting a figure of something like 80TW on a given June midday, using the average loss of albedo for the past 10 years. That might be way off; the amount of power and zeros here is way beyond what fits comfortably between my ears. Is this number remotely correct?

I just read through the Tietsche paper, and don’t see where they get “Much of this ice then survives the following summer, and sea-ice conditions can quickly return to those before the artificial perturbation.” It’s a pretty thin paper and I don’t see on what this is based. Must be the models, but what parameters determine that most of the thin new ice survives the next melt season, if the previous was warm enough to melt older thicker ice?

I’ve thought about this a (very) little further. What their models seem to say, is that even if the arctic basin contained only thin fresh new ice at the beginning of the melt season, most (or “much”) would not melt out during the summer. Even several decades from now.
Is this an assumption, or does it stand up to scrutiny?

I’ve always thought this work is largely irrelevant in any practical sense. I’m sure the science is fine, but it doesn’t really tell us anything we didn’t already know. Intuitively, it is clear that a series of cool years would result in a return of sea ice. But what is equally intuitively obvious is that subsequent warm conditions will result in more melt. Figure three confirms this.

The important point from this paper is that the ice only recovers back to the level of the GCM model and continues the decline within that scenario. I.e., so long as there is more energy coming in than going out, a few cool summers don’t mean diddly squat because the overall climate trend rules.

Yes, this might help slow the overall decline and some technocopians might think we will then find the magic answer to all this that allows us to continue to consume the resources of the planet unabated, but at the end of the day, more energy equals less ice.

If we reverse the GHG trend before the permafrost and clathrates let loose, the ice will recover. But we already knew that. This does show it can recover quickly, but the variation in the record from ’79 – ’11 also shows that. And, you’ll note in Fig. 3 it doesn’t appear to slow the trend at all. This probably reflects the growing energy being stored in the oceans and that this becomes dominant over time as the oceans get closer to their max capacity to efficiently store heat.

I don’t mean to be dismissive of the science. I know this sort of study helps refine our understanding, etc., but I think people are taking the wrong message from the work: It’s not that it can recover, it’s that it’s irrelevant if the overall problem isn’t solved.

What would be more interesting to me would be a study that showed a series of cool years via a natural cool trend (a convergence of ENSO, PDA, insolation, etc.?) might help slow or reverse the overall climate trend significantly enough for our efforts to have a chance to succeed. But the ice seems to be a feedback, not a forcing, thus is a trailing indicator overall, which means whatever the condition of the ice, the overall situation is worse than that.

Speaking as a layman, I have to say that the Tietsche, et al. paper and especially its media coverage puzzled me.

My take on the paper is exactly what ccpo(19) said: Kick the system into a new state it will relatively quickly revert to its prior path. A useful finding based on (presumably) sound science, to be sure, but not something particularly remarkable.

The main issue I had was with this notion that this finding proved there is no “tipping point” for Arctic ice.

An exogenous shock to the system — e.g. little green men show up in their spaceship and steal all the Arctic ice for their intergalactic party — seems to be such a radically different scenario from the continued warming via ghg emissions that I’m not sure why the ensuing behavior says anything about “tipping points”. Perhaps this is just a function of my not being sufficiently familiar with systems science and I’m getting too hung up on a change that arises from the inner workings of the system and one that’s imposed from the outside and not caused by state or behavior of the system. I (think I) understand what the study found — that albedo flip isn’t powerful enough to override other factors in this highly unusual scenario and hold the system in the new state. But as long as we’re still warming from the current disequilibrium and we continue to push atmospheric co2 to ever higher levels, it seems like a hollow victory.

Oh, and ditto what Michael Tobis said about Figure 2. Excellent piece of graphsmanship.

Another reason, however, is possibly the fact that we scientists have failed to make sufficiently clear that a major loss of sea ice during the early summer months is climatologically more important than a record minimum in September.

Could less and less ice in September have an increasing effect on NH weather patterns? What happens when all that heat in those huge expanses of water gets released to the atmosphere? Does it affect winter weather? Because if it does, it might not be so misdirected to focus on minimum extent in September.

And it also adds an extra dimension to the Tietsche et al paper. Sure, the ice might return and hang on for a few years after the ice pack in the Arctic Ocean melts out completely, but what will the effect be on weather patterns we depend on for agriculture?

Area, not extent, would be the controlling metric. A part of the ocean is counted in the extent metric if it has at least 15% sea ice. So, an area with 86% open sea would count in the extent metric. Sunlight wouldn’t be so finicky. If the ice isn’t there, it isn’t there.

20: “An exogenous shock to the system — e.g. little green men show up in their spaceship and steal all the Arctic ice for their intergalactic party — seems to be such a radically different scenario from the continued warming via ghg emissions that I’m not sure why the ensuing behavior says anything about “tipping points”.”

Surely it says there is no way of their being a tipping point (unless the model is missing something) because if there was a tipping point below which ice volume/extent would collapse permanently pretty much regardless of the climate situation, then you wouldn’t expect ice to bounce back so quickly, or really at all. It says that while there are some feedbacks around ice albedo and such, they aren’t big enough to lead to runaway melting, and that the ice extent/volume is more or less going to remain a function of the temperature – shown by how quickly the red lines snap back to the blue (no artifical removal) scenario.

I’m still having a hard time comprehending this. If in 2020, the little green men scoop up all the ice, by the beginning of June 2021, there will be approximately 1.7 km^2×10^6 sea ice (see Figure 3). Currently, that amount of ice melts, oh, before the end June it looks like (http://nsidc.org/data/seaice_index/images/daily_images/N_stddev_timeseries.png).
So why would there be about 4 km^2×10^6 of sea ice beginning of June in 2022 (again, Figure 3)?

IPCC climate models underestimate the decrease of the Arctic sea ice extent. The recent Arctic sea ice decline is also characterized by a rapid thinning and by an increase of sea ice kinematics (velocities and deformation rates), with both processes being coupled through positive feedbacks. In this study we show that IPCC climate models underestimate the observed thinning trend by a factor of almost 4 on average and fail to capture the associated accelerated motion.

It seems obvious the models understate the loss of extent. Per Rampal they understate ice thinning. Given that Tietsche’s results are dependent on the models, shouldn’t we be just a little bit wary?

Stuart “…while there are some feedbacks around ice albedo and such, they aren’t big enough to lead to runaway melting…”

I’ve never been much interested in this paper. I know albedo’s important, but it’s nowhere nearly as important for ice strength/weakness, melt/freeze as ocean heat content these last 10-15 years. Every current that moves into, under or through Arctic ice now is warmer than any similar body of water was 20 years ago.

If irretrievable melting occurs, it won’t be from albedo. It will be ocean waters transferring heating from 15000-20000 kms away 15-20 years ago. I think it can be avoided. I even believe it can be reversed if it happens. But neither is possible without substantially reducing CO2 concentrations, not just emissions.

I wish to point out that the statement of the sea-ice/ocean albedo feedback given above is incorrect. Sure, then the sea-ice is covered with fresh snow in winter, the albedo is high, but when summer rolls around and the surface begins to melt and form ponds, the albedo drops considerably, with measurements showing less than 40% as a large fraction of the area becomes covered by ponds. And, the albedo of water is high when the sun is high overhead at lower latitudes, but when the the zenith angle increases at high latitudes, the albedo of the ocean becomes large, as high as 30% or greater, depending on the zenith angle and the wind. For most of the melt season, the zenith angle is small, for example, at the North Pole, the sun never rises more than 23.5 degrees above the horizon and that happens only on one day. Just now, we are about 10 days from the time when sun drops below the horizon at the North Pole, not to return for 6 months. Ask anyone who has spent time aloft about sun glint or look at photos, such as those taken from the Shuttle.

Want proof? Look at these photographs taken during the SHEBA experiment.

The confusion may be the result of the frequent use of satellite photographs to present images of the sea-ice. Those photos are taken from directly overhead and do not capture the sun glint, which is reflected in a cone about the same zenith angle as the angle of incidence. Thus, the energy contained in this narrow cone is never measured. Also, the water appears very dark, because the incident light returned from the surface is that which arrives from nearly overhead and most of that is absorbed. The second photo above does capture the intensity of the reflected energy, as the camera lens is closed considerably with the effect that the floating sea-ice appears quite dark, nearly as dark as the water.

The referenced paper by Tietsche et al. needs to be carefully examined to determine just how accurately their model represents the physics. We really need to get with the program here and fix the models, which we know tend to understate the rate of decline in area which has been observed in the satellite record of extent.

Don’t forget, when the lights go out every winter, the ice ALWAYS comes back to the poles. Even in 2080, the ice will come back every winter, although it will be thin.

The poles are the Earth’s “radiators”. In winter when there is no sunlight at the poles for months on end, the only energy source into the region is the energy barreling up from the tropics and temperate regions via winds and ocean currents, which radiates into space as fast as it possibly can in the polar darkness. Daily temperature where you live falls rapidly when the sun goes down, and if the sun did not rise the next day, temperatures would continue to fall rapidly, but in polar winter the sun DOESN’T come up the next day, and so the sea and the atmosphere cool as fast as the incoming radiation from lower latitudes (yes, and ‘sensible heat’ from the ocean) will permit. Also, evaporative cooling of the ocean surface is very efficient once its radiant energy source is removed. (I recall that more than 90% of absorbed solar radiation is released back to the atmosphere through evaporation very quickly during the daily cycle. Or do I recall that wrongly?)

That is why the ice always recovers to its climatic equilibrium in a few years in the model results above – lack of sunlight in winter leads to dramatic seasonal cooling with rapid recovery of the ice AND a restoration of the ice albedo effect.

The reason that this equilibrium continues to fall through 2080 is the relentless rise of greenhouse gases. In the humid tropics, water vapor is the dominant GHG, and increasing CO2 has a relatively small effect, but at the poles in winter when it is bitterly cold, there are many orders of magnitude less water vapor, giving CO2 and other GHGs a substantial role in controlling radiant energy losses. Therefore a jump in CO2 has a big effect in slowing winter cooling at the poles, allowing the high latitude energy balance to warm to the point that there is only seasonal ice, no permanent ice.

Thanks Eli Rabett @ 3,
I wasn’t aware of Roger Pielke Sr. or his “insistence that global temperature series is an inferior metric to ocean heat content”, but I’ve held a similar opinion for some time. Looking him up I now realise he is a sceptic (I’m being polite).

The upper ocean is largely where “the climate” accumulates and redistributes heat. It is what determines the kinetics of climate change (AGW). And yes, we’ve only recently started getting a handle on measuring OHC with any precision.

That said, Pielke is obsessed with an apparent short-term pause in a long term rising trend. Like many denialists (yes he is a sceptic) he tries to make a lot out of statistical variability that favours his argument.

Whew! I’m glad that the sea ice can recover and I hope that that is correct. The bad news is BAU = sea ice gone by 2060, if anybody is still here to notice.

The figures are great and the article is easy to understand [good].

The problem remains shutting off the fossil fuel burning.

21 Neven: “what will the effect be on weather patterns we depend on for agriculture?”
We already know the answer to that from Bart Levenson: We starve in the early 2050s. Population and civilization crash.

“Does it affect winter weather?” It gets cold in the wrong places again.

22 Tony O’Brien: Look up Rossby waves. Where it is cold and where it is less cold rotate by 45 degrees longitude. “Snowmageddon” it is in the wrong places. Get used to the new norm. But you didn’t really get much snow due to GW that has already happened. Like when Rochester, N/Y. got 9 feet [108 inches] in 1 day circa 1966. Olean, N.Y. got 450 inches per year in the 1950s and now gets only 96 inches per year. It hasn’t gotten to 40 below there [straight temperature] since the 1930s.

#19 and #20. I fully agree with these comments. I believe the paper assumes that ‘artificially’ removing the ice and then the ice growing back again is not the point with respect to tipping points. The relevant issue is if some feedback that is already part of the system grows to the point where it causes much faster loss of ice. In this case, unless the feedback mechanism value can be reverted back to its original value, the sudden ice loss will indeed remain on the lower side of the tipping point. A better analogy than artificial removal of the ice and it growing back again might be the picture of a system with a cycle that follows a particular path, year on year and, due to some feedback growing to an over-riding value, enters a different cyclic path year on year. It is not going to return to the other path unless something reverses the value of the feedback mechanism. Sorry for the long post – a separate rebuttal paper might be more appropriate, but I am not a climateologist, but a mathematician.

Here’s the thing…the ice-albedo feedback mechanism may exist in isolation in a targeted climate model, but never will be found in isolation in the real world, and just as all the models prior to 2007 were projecting an ice-free summer arctic by the 2100 or later, they all were quite wrong and had to be adjusted radically sooner because of course no model can predict how a system on the edge of chaos with multiple interrelated feedbacks will actually progress…i.e. none of them can predict the true tipping points, and this new model is no different. For example, the study did not take into account continued increases in ocean temperatures of water entering the Arctic (as they have been for many years), nor of course, the likely continued increases in methane in the atmosphere, at least partially being created by the same warming of those arctic waters.

In my opinion, the most accurate way to see what the likely future of Arctic sea ice will be is to use the models only as rough guides (accepting that modelling a system on the edge of chaos will always fail to see the tipping points), and rather, to look to the Earth’s past, when similar climate dynamics existed. In this case, we are led to the mid-Pliocene at least and perhaps further back to even warmer climates. In such scenarios, multiple (and not completely understood feedbacks) create the conditions for the Arctic to be ice-free or nearly so year round, Greenland and Antarctica lose most, if not all, of their glacial ice, and the world to be a vastly different place. So, while it’s nice to look at very specific isolated models, they are more an exercise in precise and confined modelling, as opposed to creating a realistic scenario of the real climate under multiple interrelated feedbacks. Only looking at past similar climates can give us the best glimpse of what happens in the real world of a climate system on the edge of chaos.

@Alex Thomas
“The ice volume change is less relevant to the ice-albedo feedback, where the relative proportions of ice covered to ice free ocean dominate the radiative effect…”

Alex, I can only agree. A simple thought experment shows that it matters little to albedo if the ice is 1 cm or 10 metres thick.

What does concern me though is the thermal forcing is only getting worse; that is there is little prospect of a reduction in radiative forcing (“an efficient reduction of CO2 emissions”), or a reduction in heat transfer from the local water (presumably related to ocean heat content).

I simply don’t believe the blue line in Figure 3 above. I’ve yet to see a GCM that is skillful in predicting Arctic sea ice loss or what is happening to the cryosphere in general. I’m not a climate scientist so maybe I’m not in touch. Please correct me if necessary.

Furthermore, I think the main point of the Tietsche paper is lost in the post above. That is, assuming their GCM is accurate, arctic ice loss does not exhibit hysteresis – it is fully and rapidly recoverable when favourable conditions return. That is, it does not constitute a “tipping point”.

@ JBar,
“Don’t forget, when the lights go out every winter, the ice ALWAYS comes back to the poles. Even in 2080, the ice will come back every winter, although it will be thin…”

Well, no. If it were that simple, all regions where ocean is exposed to the polar night would form an ice cover. Not all do, as it depends on the energy balance. If, due to ocean heating and ocean currents, the water temperature remains subtantially above zero in the Arctic, an ice cap will not form even at the North Pole in mid-winter. This has been the case in the distant past.

Bruce@38: the great majority of ocean exposed to polar night does indeed form an ice cover. The main exception north of 70N is areas of the Greenland and Barents Seas, where warm surface waters from the Atlantic can (in some years) prevent freezing. But in the Arctic Ocean proper, everything freezes. Even waters which have melted early in the season and thus been exposed to continuous solar heating for months still freeze over. Look at the winter of 2007/2008. The Arctic Ocean needs to get a *lot* warmer before this is prevented.

Re #30:
A minor correction, the angle of the sun above the horizon is the solar elevation angle, the solar zenith angle is the angle measured from nadir to the sun.

Not sure why you think sun glint is important. Glint occurs with a more or less unique but transient alignment of solar zenith and solar azimuth, wind and wave direction relative to the solar angles, and, finally, the viewing angle of the sensor relative to the sun and the waves. Few visual wavelength satellites sensors “see” above about 82 N (northern edge of Greenland) or 82 S.

Re #13 Andy and #31 JBar
Regarding radiators and wind — I see the minimum area as quite an important factor. I used to harp on about June ice coverage as being the most significant thing to watch and report on, rather than the September minimum. But the blogs taught me better and the Tietsche et al Fig 3 is instructive. How can we turn this to our advantage?

Well, maybe we can use wind to upgrade the radiator … in winter. What if ice area can be reduced, to decrease the winter insulation and increase heat loss from the Arctic Ocean to the long night? Instead of Figure 3 above (in which sea ice is disappeared in June), what if sea ice can be disappeared (or compressed) in winter — every year? Can we lose enough energy to space to slow the warming of the planet?

Schröder and Connolley [2007], who showed that sea ice
recovers from a complete removal within a few years.
However, they restricted their experiments to a preindustrial
climate and did not address the mechanisms of the sea-ice
recovery.

“I just read through the Tietsche paper, and don’t see where they get “Much of this ice then survives the following summer, and sea-ice conditions can quickly return to those before the artificial perturbation.””

It plainly says the paper shows model based calculations. Of course you don’t see all the equations written in computer code unless you study the model separately.

“I’ve always thought this work is largely irrelevant in any practical sense. I’m sure the science is fine, but it doesn’t really tell us anything we didn’t already know. Intuitively, it is clear that a series of cool years would result in a return of sea ice.”

1)The reason scientists do research is that “intuitively clear” might leave you in ignorance of Newton’s laws for thousands of years.
2) The paper is not about removal of sea ice followed by a cooler climate. It is about continuing nearly the same climate, just without, say, the unusual Arctic weather of 2007.

“The referenced paper by Tietsche et al. needs to be carefully examined to determine just how accurately their model represents the physics.”

Not a chance. The paper says on page 1

Here, we report the recovery of the Arctic from
a prescribed loss of summer sea ice in the AOGCM
ECHAM5/MPI-OM at different times ….

You may study the physics of this standard model separately if you wish, but first I recommend understanding the paper as such.

Enough of comments. What of the paper? From page 1 again:

A valuable tool for understanding those mechanisms
are experiments which perturb Arctic sea!ice conditions
systematically. To our knowledge, this sea!ice perturbation
approach in an AOGCM has so far only been applied by
Schröder and Connolley [2007], who showed that sea ice
recovers from a complete removal within a few years.
However, they restricted their experiments to a preindustrial
climate and did not address the mechanisms of the sea-ice
recovery.

Here, we report the recovery of the Arctic from
a prescribed loss of summer sea ice in the AOGCM
ECHAM5/MPI-OM different times during the 21st century,
and investigate the mechanisms of recovery by analyzing the
Arctic energy budget. In these perturbation experiments, the
initial conditions are such that the ice–albedo feedback, as well
as the other feedbacks related to sea-ice anomalies, are most
pronounced. Thus, these experiments answer the question of
whether perturbations of sea-ice cover alone are able to trigger

I submit that this type of perturbation experiment (be thankful it is done within a model, not in vivo) is very worthwhile.

Meanwhile what of the Arctic? Arctic amplification of global warming is occurring at the pace of the US Navy’s Arctic regional model, which is to say quite a bit faster than in the global models. The Arctic is changing quickly enough so that the climate which the sea ice would recover to in three years is warmer than the climate of the sea ice removal in year one of the model runs. Thus in practice so far, recovery is to a lower quantity of ice. The reductions in ice volume, area and extent so far indicate that we will reach the point that the weather of 2007 is not needed to clear the ice in September sooner than the global models predict. It would be interesting to run the model experiment in the Naval model.

Nick Barnes says:
10 Sep 2011 at 2:53 AM
Jathanon@25: Consider, how much ice would there be at the end of March 2022?

There would be more than the June 1, 2022 point of course. How much their model has at time we don’t know. However, consider that
1. No ice on June 1, 2020
2. Ice grows again during winter 2020-21
3. Ice is at 1.7 on June 1, 2021
4. Ice melts out maybe by July 1, 2021
5. Ice grows again during winter 2021-22
Now, why would considerably more ice grow this winter, starting from a no ice condition in mid-summer? When “large amounts of heat indeed accumulate in the ocean during the ice-free summer. However, this heat is efficiently released to the cold atmosphere already during the following autumn and winter.”
To me, it sounds like after removal, every following year would have around 1.7, melting out and starting over.

Schröder and Connolley [2007], who showed that sea ice
recovers from a complete removal within a few years.
However, they restricted their experiments to a preindustrial
climate and did not address the mechanisms of the sea-ice
recovery.

“I just read through the Tietsche paper, and don’t see where they get “Much of this ice then survives the following summer, and sea-ice conditions can quickly return to those before the artificial perturbation.””

It plainly says the paper shows model based calculations. Of course you don’t see all the equations written in computer code unless you study model separately.

“I’ve always thought this work is largely irrelevant in any practical sense. I’m sure the science is fine, but it doesn’t really tell us anything we didn’t already know. Intuitively, it is clear that a series of cool years would result in a return of sea ice.”

1)The reason scientists do research is that “intuitively clear” might leave you in ignorance of Newton’s laws for thousands of years.
2) The paper is not about removal of sea ice followed by a cooler climate. It is about continuing nearly the same climate, just without, say, the unusual Arctic weather of 2007.

“The referenced paper by Tietsche et al. needs to be carefully examined to determine just how accurately their model represents the physics.”

Not a chance. The paper says

Here, we report the recovery of the Arctic from
a prescribed loss of summer sea ice in the AOGCM
ECHAM5/MPI-OM at different times

You may study that standard model separately if you wish, but first I recommend understanding the paper as such.

Enough of comments. What of the paper? From page 1 again:

A valuable tool for understanding those mechanisms
are experiments which perturb Arctic sea-ice conditions
systematically. To our knowledge, this sea-ice perturbation
approach in an AOGCM has so far only been applied by
Schröder and Connolley [2007], who showed that sea ice
recovers from a complete removal within a few years.
However, they restricted their experiments to a preindustrial
climate and did not address the mechanisms of the sea-ice
recovery.

Here, we report the recovery of the Arctic from
a prescribed loss of summer sea ice in the AOGCM
ECHAM5/MPI-OM different times during the 21st century,
and investigate the mechanisms of recovery by analyzing the
Arctic energy budget. In these perturbation experiments, the
initial conditions are such that the ice–albedo feedback, as well
as the other feedbacks related to sea-ice anomalies, are most
pronounced. Thus, these experiments answer the question of
whether perturbations of sea-ice cover alone are able to trigger

I submit that this type of perturbation experiment (be thankful it is done within a model, not in vivo) is very worthwhile.

Meanwhile what of the Arctic? Arctic amplification of global warming is occurring at the pace of the US Navy’s Arctic regional model, which is to say quite a bit faster than in the global models. The Arctic is changing quickly enough so that the climate which the sea ice would recover to in three years is warmer than the climate of the sea ice removal in year one of the model runs. Thus in practice so far, recovery is to a lower quantity of ice. The reductions in ice volume, area and extent so far indicate that we will reach the point that the weather of 2007 is not needed to clear the ice in September sooner than the global models predict. It would be interesting to run the model experiment in the Naval model.

RE # 42, BillS mentions the difference between solar elevation and zenith angle. At the North Pole, the elevation never exceeds 23.5, thus the zenith angle never falls below (90 – 23.5) = 66.5 degrees. The reason sun glint is important is that water, like any transparent media, becomes highly reflective as the angle of incidence (aka, the zenith angle) approaches 90 degrees. On clear days, much of the energy arrives in the direct beam and much of that will tend to be reflected from the water’s surface. The effect is also a function of wave height and wave height is a function of wind speed (mol) for the open ocean. On cloudy days, the clouds scatter the light and thus the albedo may be higher, but the clouds also reflect some fraction of the light back to space, so the net energy entering the ocean may not be so great. Here’s a graph of ocean albedo taken from a report by Payne, written in 1972, in which the author presented data from measurements taken from an old platform in the ocean:

It’s worth mentioning that the satellite sensors used to measure radiant energy over the poles can not directly view the energy in the sun glint because of the angles involved. For example, the present AQUA and TERRA satellites do not cover the Arctic at times of the day when any sun glint is likely to be within view of the sensors. Your reference to an 82 degree limit applies to the ground track, but instruments such as CERES scan cross track to cover higher latitudes as the ground track turns briefly east-west.

TERRA has an equator crossing at 10:30 AM local time, but the highest latitude is crossed 6 hours earlier in local time at 4:30 AM. The AQUA orbit equatorial crossing is at 1:30 PM local time, the highest latitude time is 6 hours earlier at 8:30 AM, AIUI. One can look at various orbit track times for both satellites here, to add to the confusion:

5 Alex says, “The ice volume change is less relevant to the ice-albedo feedback, where the relative proportions of ice covered to ice free ocean dominate the radiative effect. Reducing ice thickness (volume) will serve to make the system more sensitive to melting (and further area loss and radiative feedback) but as mentioned in the Tietsche et al paper this will be rapidly recovered from.”

You fail to understand that volume is incredibly important to the date of ice loss for the next year. Thin ice melts out earlier, and since the albedo effect is most important early in the summer, thinning of ice becomes quite important to feedbacks.